As NFL teams begin the usually smooth process of signing their draft picks, some are running into resistance from the players’ union, which urged agents in a memo last month to reject provisions it says are prohibited from rookie contracts under the collective bargaining agreement.

The NFL Players Association argues that contract provisions regarding how teams may collect money that players owe them, when players are required to pass a physical, whether they must disclose changes in their health and other issues aren’t expressly permitted under the 2011 CBA and thus cannot be included in contracts, even if they’ve been incorporated in the past. And multiple NFL executives and agents say that has slowed down negotiations with certain clubs.

“The collective bargaining agreement protects players from bad language that clubs would insert into rookie player contracts,” George Atallah, the union’s assistant executive director of external affairs, told USA TODAY Sports on Friday. “We negotiated that clause to keep teams from taking advantage of players and agents. The NFLPA will take action against any club that violates Article 7 of the CBA.”

In essence, the 2011 CBA “slotted” draft pick contracts, so there’s little room to haggle over money, and holdouts are rare. (Last year’s standoff between the Chargers and defensive end Joey Bosa was over payment schedule and the use of so-called “offset” language.) The Carolina Panthers have already signed their entire seven-man draft class, including first-round running back Christian McCaffrey. The San Francisco 49ers have signed six draft picks, and the Green Bay Packers five.

But each team uses its own standard contract language, which has put some clubs in the NFLPA’s crosshairs.

Executives from two teams, speaking with USA TODAY Sports on condition of anonymity because they’re not authorized to comment publicly, said they believe the union is misinterpreting Article 7, Section 3 (c), which lays out 13 permissible terms that don’t involve compensation, such as promotional appearances, workers compensation, insurance policies, etc.

“The union is arguing that, if you put something in your language that doesn’t fall directly within those 13 things, it’s prohibited,” one of the executives said. “The league’s position is it’s not limited in scope to those specific 13 things — those are just examples of non-compensation terms, but they’re not definitive that you can’t go outside those.”

Brian McCarthy, the NFL’s vice president of communications, wrote in an email: “In addition to comp terms, a rookie contract may also contain non-compensation terms ‘relating to’ a wide variety of issues. That section (of the CBA) does not specify the scope or content of such provisions. It permits the agent/player and club to reach agreement on such matters.”

It’s unlikely this dispute will cause any player to miss time. But it could lead to a grievance down the line and presents an extra hurdle for some teams and agents in negotiations, at a time when few hurdles with rookie deals remain.

The union’s April 29 memo lists examples of “prohibited provisions” that teams attempted to include in rookie contracts last year.

“Per the CBA, if an impermissible term is included in a rookie contract, it is void ab initio and of no legal effect,” the memo said. “However, even though such terms are void, no agent is permitted nor authorized to include any prohibited term in a rookie contract.”

Article 7, Section 3 (d) identifies prohibited terms in rookie contracts, but those all deal with compensation: option bonuses, option exercise/non-exercise fees, most salary advances, voidable year provisions, buybacks and any “contract within the contract” that would supersede the deal.